1. Field of the Invention
This invention relates to a method and a device for making an optical plate formed with a microstructure.
2. Description of the Related Art
As shown in FIG. 1, Japanese Patent Publication No. 2001-113538 discloses a method for making an optical film formed with a microstructure. The method includes: (a) reeling out an substrate material 1; (b) applying an ultraviolet photosensitive resin 10 to a surface of the substrate material 1; (c) advancing the substrate material 1 and the ultraviolet photosensitive resin 10 applied onto the substrate material 1 through a pair of pressing rollers 11, one of which having a micropatterned surface, so as to form an optical film formed with a microstructure 13; and (d) irradiating and curing the ultraviolet photosensitive resin 10 of the optical film using an irradiation apparatus 12.
To be specific, when the substrate material 1 and the ultraviolet photosensitive resin 10 pass through the pressing rollers 11, the ultraviolet photosensitive resin 10 is subjected to a pressing force from the pressing rollers 11 and fills into grooves of the micropattern thereof, followed by curing of the ultraviolet photosensitive resin 10 using the irradiation apparatus 12 so as to form the microstructure 13 on the substrate material 1. In the Japanese publication, since the combined thickness of the substrate material 1 and the ultraviolet photosensitive resin 10 is relatively small, i.e., less than 0.3 mm, the substrate material 1 and the ultraviolet photosensitive resin 10 have good flexibility and can be flexed to contact intimately the pressing rollers 11.
However, as for an optical plate which is generally used in a backlight module of a liquid crystal display and which has a relatively larger thickness than that of the optical film of the above Japanese Patent Publication and thus has a relatively inferior flexibility, such as a light diffusion plate or a light guide plate, the substrate material 1 applied with the ultraviolet photosensitive resin 10 might not be able to contact intimately the surfaces of the pressing rollers 11. Moreover, since the substrate material 1 may not be in intimate contact with the pressing rollers 11, the ultraviolet photosensitive resin 10 applied thereon might not be completely pressed by the micropatterned surface of the rollers 11. Therefore, transfer of the micropattern of the pressing rollers 11 to the microstructure of the optical plate is likely to be incomplete, i.e., defective microstructure, and thus has a poor transferring rate.